A constant temperature liquid circulation apparatus which heats or cools a load by supplying temperature-adjusted constant temperature liquid to the load is known, as described in PTL 1, a Japanese Unexamined Patent Application Publication No. 2003-028515, for example. As schematically illustrated in FIG. 3, a constant temperature liquid circulation apparatus generally includes a constant temperature liquid circuit 41 which circularly supplies a constant temperature liquid which temperature has been adjusted to a load 40, a refrigeration circuit 42 which adjusts the temperature of the constant temperature liquid, and a control unit 43 which controls the overall device.
The constant temperature liquid circuit 41 includes a tank 44 which accommodates the constant temperature liquid, a pump 45 which supplies the constant temperature liquid within the tank 44 to the load 40, and a temperature sensor 46 which measures the temperature of the constant temperature liquid supplied to the load 40. The refrigeration circuit 42 includes a compressor 47 which compresses the coolant in a gaseous state into a high-temperature high-pressure gaseous coolant, a condenser 48 which cools the high-temperature high-pressure gaseous coolant fed from the compressor 47 so as to be a high-pressure liquid coolant, a first electronic expansion valve 49 which expands the high-pressure liquid coolant fed from the condenser 48 so as to be a low-temperature low-pressure liquid coolant, and an evaporator 50 which evaporates the low-temperature low-pressure liquid coolant fed from the first electronic expansion valve 49, by thermal exchange with the constant temperature liquid, so as to be a low-pressure gaseous coolant, and which low-pressure gaseous coolant is then fed to the compressor 47.
The control unit 43 then controls the opening angle of the first electronic expansion valve 49, rotations of the compressor 47, and so forth, in accordance with the temperature of the constant temperature liquid measured by the temperature sensor 46, and adjusts the flow rate of coolant supplied to the evaporator 50, thereby adjusting the temperature of the constant temperature liquid so as to be closer to the set temperature.
On the other hand, with this type of constant temperature liquid circulation apparatus, when the compressor goes from an off state to an on state, if the pressure difference between the high pressure side (out port side) and low pressure side (in port side) of the compressor 47 is great, the compressor 47 cannot be activated due to overload. Accordingly, when the compressor 47 is in the off state, time needs to be allowed for the coolant to flow from the high pressure side to the lower pressure side so that the pressure difference is smaller (pressure equalizing operation time), thereafter which the compressor 47 can be turned on. This pressure equalizing operation time is generally around several minutes.
However, the refrigeration circuit 42 cannot run during this pressure equalizing operation time, so the rise in temperature of the constant temperature liquid due to the load 40 is great, which poses various problems for subsequent cooling or heating of the load 40.
Accordingly, the above-described constant temperature liquid circulation apparatus is provided with a bypass channel 51 connecting the high pressure side and low pressure side (out port side of the first electronic expansion valve 49) of the compressor 47, and a second electronic expansion valve 52 is connected to the bypass channel 51, so that when the compressor 47 turns off, this second electronic expansion valve 52 is opened such that part of the gaseous coolant at the high pressure side of the compressor 47 flows to the lower pressure side of the compressor 47, thus speeding up the pressure equalizing operation.
However, increased costs of the device and increased complexity of the structure is unavoidable when employing such a configuration for the pressure equalizing operation, since the electronic expansion valve 52 is expensive, and the bypass channel 51 also needs to be provided.